INFLUENCE OF EXERCISE-INDUCED MYOCARDIAL-ISCHEMIA ON RIGHT-VENTRICULAR DP DT - POTENTIAL IMPLICATIONS FOR RATE-RESPONSIVE PACING/

Background: Right ventricular(RV) dP/dt(max) has been used as a simple parameter for rate responsive pacing to simulate the normal sinus nod e function. However, the effect of acute myocardial ischemia on RV dP/ dt(max) has not yet been evaluated. Methods: RV high fidelity pressure was measured in 21 patients at rest and during supine bicycle exercis e. Nine patients (Group 1 = controls) had no or only minimal alteratio ns of the coronary arteries and 12 (Group 2 = CAD) had significant cor onary artery disease with exercise induced left ventricular (LV) wall- motion abnormalities (n = 10) and/or angina pectoris (n = 6). RV press ure and its first derivative (RV dP/dt) were determined by an 8 French micromanometer catheter. The time constant of RV pressure decay (Tau) was calculated from the negative reciprocal of RV pressure versus neg ative dP/dt during isovolumic relaxation. RV volumes and ejection frac tion were calculated from RV biplane angiograms (multiple slice method ) at rest and during exercise. Results: Heart rate (HR), RV dP/dt(max) and dP/dt(min) increased significantly during exercise, whereas Tau d ecreased. There were no significant differences between the two groups , although RV ejection fraction increased from 67% to 72% in the contr ol group but decreased from 63% to 51% in the CAD group (P < 0.05). An exponential relationship was found between HR and dP/dt(max) with a c orrelation coefficient of 0.82 (P < 0.01; SEE = 7% of the mean value). Conclusions: Acute exercise induced myocardial ischemia does not sign ificantly influence RV dP/dt(max) during sinus rhythm. Consequently, t his index of RV contractility may be used in patients with coronary ar tery disease as a simple parameter for rate responsive pacing.